The present invention relates to a molding machine, and more particularly to a mix head assembly for a molding machine that thoroughly mixes a multiple of fluid material components.
Many molding machines provide for the mixing of at least two fluid materials to form a hardenable or settable mixture which can be discharged into a mold cavity in the formation of an article molded of synthetic resin. One particular mixture includes three components, a catalyst, a matrix polymer and a foaming agent.
The fluid materials are typically fed from a supply by a delivery or feed assembly which communicates with a mixing head. Each fluid material is mixed by the mixing head and discharged into the mold cavity to form the molded article.
An important aspect of the molding process is the thoroughness of mixture of each fluid material in the mixing head during each cycle of the molding machine. Each fluid material must be efficiently mixed at the mix head to assure homogenous composition of the finished material. It is also desirable to provide a flushing assembly within the mix head to minimize the possibility of fluid material components remaining and curing within the mix head.
A mix head assembly according to the present invention generally includes an output chamber assembly, a main body assembly, and a drive assembly. The main body assembly preferably includes a plurality of inlet ports which correspond to the number of fluid material supplies. The fluid material from each fluid material supply is received through the input ports, thoroughly mixed within the mix head assembly, and output through the output chamber assembly into a mold assembly.
The drive assembly includes a drive motor which rotatably drives a main shaft which propels a plurality of impellers. The impellers preferably rotate within a secondary chamber and a tertiary chamber.
Each inlet port includes a moveable gate to open and close fluid material flow through the input ports. The gates are preferably mounted to a retaining block. A flush actuator plate is mounted to a flush push plate by a plurality of flush actuator rods. The flush actuator rods remotely drive the flush actuator plate along a main axis of the mix head assembly. The retaining block drives the gates within respective feed chambers of to selectively provide or prevent communication from each inlet port to the output chamber assembly and impellers.
In one disclosed embodiment the mix head assembly include a flush assembly to communicate a flushing fluid from a supply through the gates and into the feed chambers to minimize residual fluid material after each molding cycle. A flush input communicates with a flush bore located axially through the gate. A flush pin is movably located within the flush bore such that the flush pin selectively provide or prevents communication from the flush input into the feed chamber.
In operation, a plurality of flush actuator rods remotely drive a flush actuator plate toward the retaining block. As the flush actuator plate is driven toward the retaining block, the flush actuator plate overcomes a biasing member such that the flush pin extends from the head of the gate. The flush bore opens to the feed chamber and a complete communication path for a flushing fluid or the like is thereby created from the flush inlet, through the flush bore, and into the feed chamber. Although the flush fluid path is preferably opened in response to operation of the flush actuator plate, it will be realized that the flushing fluid can be selectively injected into the flush input under control of a controller.
Further movement of the flush actuator rods, remotely drives the flush actuator plate against the retaining block. The retaining block and gates are thereby driven as a complete unit such that the gates selectively block the feed chamber. As each gate is fixed in the retaining block, the gates operate in unison such that that the inlet ports are opened and closed substantially simultaneously.
As the fluid material from each fluid material supply exit the respective feed chambers, the fluid materials encounter a first impeller in the tertiary chamber. Preferably, the first impeller is angled relative to the drive shaft such that the impeller drives the fluid materials back toward the feed chambers. Effective mixing of the fluid materials is thus provided as the fluid materials are driven back into the streams of fluid materials from the feed chambers.
The next impeller which the fluid material flow encounters preferably has an opposite pitch such that the second impeller drives the fluid material toward a third impeller. Sequentially alternating between this xe2x80x9cwith streamxe2x80x9d and xe2x80x9cagainst streamxe2x80x9d impeller drive orientation preferably continues until the final impeller drives the fluid materials out through the through a first chamber portion where dividers provide a final fluid material flow disturbance as the fluid material is directed to the mold assembly.
This mix head is particularly advantageous for mixing a material to be injected wherein a polymer matrix carries glass fibers. The applicant of this invention has recently also invented the concept of a coated glass fiber with a coating that prevents the fibers from beginning to react with the other components. To assure the coated fibers react with the other components, the coating is efficiently smashed or cracked in the mixing head by the impellers. The fibers then begin to react.